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Anguilla dieffenbachii
Anguilla dieffenbachii (''New Zealand longfin eel)' Kingdom: '''Animalia Phylum: Chordata Class: Actinopterygii Order: Anguilliformes Family: Anguillidae Genus: Anguilla Species: Anguilla dieffenbachii Environment: milieu, climate zone, depth range, distribution range: Marine; freshwater; brackish; demersal; catadromous. Subtropical; 34°S - 47°S. Distribution: Southwest Pacific: endemic to New Zealand. Size, weight, age: Max. length: 1.85 m (male), 1.56 m (female), common length: 1 m; weight: 25 kg; age: ?''' ''Short description:'' The easiest way to identify the longfin eel is by the length of its fins: the dorsal (top) fin is about two-thirds the length of the body and starts significantly further towards the head than the anal (bottom) fin. In the shortfin eel the fins are of similar length. When a longfin eel bends its loose skin wrinkles distinctively inside each bend, where a shortfin eel's skin is smooth. A longfin's mouth extends past its eyes, further than a shortfin's. Female longfin eels are larger and longer-lived than males. Males average 66.6 cm but reach up to 73.5 cm in length, with an average age of 23 years (12–35 years). Females are considerably larger, ranging from 73–156 cm with an average length of 115 cm. Females attain an age of 20 to 60 years before migrating to sea to breed. Longfin eels in the North Island migrate at a younger age and thus have faster generation times. Determining longfin sex is difficult as their sexual organs are not determined until they are over 45 cm in length. The only method to determine longfin eels sex is through internal examination and only becomes easy to distinguish when the eels mature and migrate. ''Biology:'' Commonly found in lakes and rivers. Inhabits stony rivers. Migrates to the sea to breed. Oviparous. Marketed fresh, smoked and frozen; eaten fried and broiled. Reports of reaching up to 2 meters and 50 kilograms are rare and more common historically; in recent times, only a few exceed 120 cm TL. ''Life cycle and mating behavior:'' Like other members of the Anguillidae, longfin eels have a rather unusual life cycle: they grow and mature into fertile adults in fresh water, then migrate to the sea to breed. This catadromous breeding system also ensures randomised mating, creating a panmictic population. The New Zealand longfin eel is a very long-lived fish, with records of females reaching 106 years old and weighing up to 24 kg. They have the slowest growth rate of any eel species studied, just 1–2 centimetres a year. Longfin eels life cycle like other species of Anguillidae eels is rather complex consisting of four distinct life stages which remained a mystery for many decades and still is not fully understood. New Zealand longfins breed only once at the end of their lives, making a journey of thousands of kilometres from New Zealand to their spawning grounds near Tonga. Their eggs (of which each female eel produces between 1 and 20 million) are fertilized in an unknown manner, but probably in deep tropical water. The mature eels then die, their eggs floating to the surface to hatch into very flat leaf-like larvae (called leptocephalus) that then drift along large oceanic currents back to New Zealand. This drifting is thought to take up to 15 months. There have been no recorded captures of either the eggs or larvae of Longfin eels. Upon arriving in New Zealand, the larvae undergo a transformation (metamorphosis) into glass eels, like small transparent adult eels. These occupy estuaries for their first year, during which they develop colouration and become elvers, which resemble small adult longfin eels. The elvers migrate upstream, where they develop into adults. The recruitment of glass eels into New Zealand's freshwater river networks is a very variable process, thought to be affected by the El Niño and La Niña Southern Oscillations. This is a major reason for the failure of longfin eel aquaculture in the 1970s. Oviparous. ''Main reference:'' '''Armitage, R.O., D.A. Payne, G.J. Lockley, H.M. Currie, R.L. Colban, B.G. Lamb and L.J. Paul (eds.), 1994. Guide book to New Zealand commercial fish species. Revised edition. New Zealand Fishing Industry Board, Wellington, New Zealand, 216 p. IUCN Red List Status: Not Evaluated CITES: Not Evaluated CMS: Not Evaluated Threat to humans: Harmless Human uses: Fisheries: commercial; aquaculture: experimental. Category:Anguillidae, Freshwater eels